The ultimate purpose of both the within- and between-groups comparisons in mental health disparities research is to assess whether or not social stress is a cause of mental health problems and, if so, to explain the processes through which it works. To fully describe social stress as a cause, researchers would need to demonstrate that disadvantaged status is related to higher incidence of mental disorders or higher mean levels of mental health problems (using the between-groups analyses) and that putative social stress processes (such as perceived discrimination) affect mental health outcomes and explain the disparity.
As with most epidemiologic approaches, analyses of the total effect (between-groups differences in level of mental health problems) can, in the absence of bias, identify that an exposure is a cause, but it does not explain how the cause works. (Shadish, Cook and Campbell 2002
). Applied to health disparities, between-groups analyses can show a causal effect of disadvantaged group status but leaves unexamined the pathways through which disadvantage has an effect. In contrast, studies of the social stress process typically use within-group analysis that can capture the workings of stress, but not its differential effect (Clark et al., 1999
; Meyer, 2003b
A study that examines both within- and between-groups variance is necessary to test the total mediational hypothesis described in . Taylor and Turner (2002)
provide an example of such a study. They found elevated levels of depressive symptoms for young African Americans compared with whites and found that this difference was explained, at least in part, by exposure to social stress.1
Whether a single study has the data needed to conduct a full mediational analysis, or whether the data come from separate studies, researchers need to examine convergences and divergences from within- and between-groups analyses. Because within and between-groups analyses use different comparison groups to simulate the causal contrast, measure different aspects of social stress constructs, and pose different methodological challenges, the results from these two types of studies may differ. The difference between what we can infer from these methodologies can be exploited for a fuller understanding of the effect of social stress on mental health.
There are four possible combinations of evidence from the two types of studies: there could be consistent evidence in support or in refutation of social stress hypotheses from both types of studies, or there could be inconsistent evidence with results from within-group studies supporting and results from between-groups studies refuting social stress hypotheses, or vice versa.
The strongest evidence for an etiologic role of social stress on health is a convergence of findings that show more distress or disorder for the disadvantaged group in the between-groups comparison and more distress or disorder for people with a greater level of social stress in the within-group comparison. This provides evidence for a mental health disparity and evidence that the disparity is related to social stress processes (e.g., prejudice and discrimination).
Other studies found this pattern in the case of lesbians, gay men and bisexuals vs. heterosexual populations (Meyer, 2003b
). Such convergence of findings provides stronger support for the social stress hypothesis than do results from one study design alone because the probability of both types of studies giving a false positive result is lower than the probability for false results from each type of study alone. However, as we noted in the introduction, social stress theory is not about the relationship between a particular social group and mental health but rather the relationship between the category of disadvantaged group status and mental health. For the theory to be supported this pattern of results should adhere to the preponderance of disadvantaged groups. The evidence does not support this conclusion.
Mixed results from the two types of analyses, especially in the case of African Americans and women, are more common. Most common are results showing that stressors affect mental health problems in within-group analyses (e.g., greater exposure to perceived discrimination is related to more symptoms of depression) in the absence of results showing a main effect in between-groups analyses (e.g., African Americans and whites have the same disorder prevalence).
An important question is what explains this inconsistency. One explanation is that methodological limitations of between-groups studies are more severe than the methodological limitations of within-group designs. Another explanation is that while disadvantaged status causes excess stress, resilience and coping of disadvantaged groups mitigate the impact of this stress (Clark et. al. 1999
), in effect canceling each other, leading to the observed results of no difference between groups. This would be an example of mediation in the face of a suppressed main effect (Shrout and Bolger 2002
: MacKinnon et al. 2006). But this explanation is questionable on theoretical grounds. We disagree that a stressor so perfectly embedded in its remedy can be conceptualized as a causal factor. That is, if social disadvantage contains both a cause and a cure in equal proportions, can we say that the social disadvantage causes mental disorders? Indeed, social stress theory is often framed in terms of the maldistribution of both stressors and
coping resources across social status groups (Pearlin, 1989
). Therefore, the very notion that a disadvantaged social group fares better than the advantaged group in availability of coping resources contradicts social stress theory.
We must also consider explanations that accept both sets of results as valid, and consider that the conclusion to be drawn from this inconsistency leads to refutation of social stress theory. With few exceptions (e.g., Sellers and Shelton 2003
), researchers do not consider such a conclusion.
Oddly, the interpretational challenge posed by inconsistent findings in between-and within-group analyses can go unrecognized even in studies that examine both. For example, Kessler et al. (1999)
and Williams et al. (1997)
, failed to find the prerequisite between-groups disparity—the disadvantaged social group, African-Americans did not
have elevated disorder prevalence compared with Whites. Yet, in both papers the authors continued to examine exposure and reactivity to perceived discrimination as a potential causal factor—a mediator in the relationship of disadvantaged social status and mental disorder. Clearly, however, social stress cannot be a cause of a disparity if no disparity has been documented. As we illustrated in , disparities in outcome is a condition for showing a mediational effect in the causal relationship of social structures and mental health problems. We find it perplexing that while there is growing recognition in the field that there is no racial mental health disparity (e.g., Kessler et al. 1999
; Williams et al. 2007
; Schulz et al., 2000
), researchers continue to suggest that discrimination is a mediational process that explains mental health disparities. The implications for social stress theory of such inconsistencies are rarely discussed.
To better investigate the causal role of social stress in health disparities it is important to examine all aspects of the social stress model as it is reflected in evidence from both within- and between-groups analyses. If we accept as valid the preponderance of evidence in between-groups studies of African Americans vs. whites and women vs. men, then a reasonable interpretation is that social disadvantage does not cause mental disorders in these populations. Consistent with the findings from within-group analyses, we may conclude that the appraisal and experience of stress rather than the structural stress has etiologic significance for mental disorders. That the results of these two types of analyses may validly differ is consistent with Rose’s (1992)
important insight that the causes of variation between groups may be different from the causes of variation within groups. Within-group analyses can easily miss or misattribute the causes of health disparities by focusing on the individual and ignoring the etiologic context (Krieger, 2000
; Schwartz & Carpenter 1999
Holding on to a theoretical perspective without sufficient evidence leads to stagnation in science because “a theory that cannot be mortally endangered cannot be alive” (Platt 1964
:349). As a starting point to further our understanding of stress theory, researchers should examine the discrepancy in results from the two approaches to the study of health disparities and design studies that would explicitly address plausible alternative explanations for the observed discrepancies. For example, studies could test whether reporting bias explains the relationship of perceived discrimination and mental disorder found in within-group studies by comparing results from studies that use self-report vs. objective ratings of discrimination (Dohrenwend et al. 1993
). If the use of objective ratings decreases the discrimination-mental disorder association, then reporting bias would be supported as an explanation for the discrepancy. Alternately, the hypothesis of unreliability of the mental health measure among the disadvantaged group obscuring the association in between-groups studies could be examined through a series of sensitivity analyses to see the viability of this explanation (Phillips 2003
Researchers may otherwise choose to reformulate the theory itself. As we described above, such reformulation has led to theorizing about the role of gender in internalizing and externalizing disorders (Rosenfield, 1999
). Another approach may be to redefine social categories of disadvantage. Intersectionality suggests that intersections of group characteristics, such as poor women, form categories whose social meaning cannot be captured by the disparate elements of the intersection (Glenn, 2001). It is possible that conceptualizing social groups in terms of intersections could help refine social stress hypotheses (Meyer, Schwartz, & Frost, 2008
). Some work on intersections shows it to be a promising conceptual tool for refining epidemiological predictions (Mccall 2005
). However researchers approach this problem, they must start by recognizing inconsistencies in the evidence and proposing new directions for study. We hope that this paper will encourage such new thinking.